Heat exchangers are often comprised of a multiplicity of heat exchange tubes which extend between and are generally supported by at least one tube sheet or plate. The tube sheet has a series of holes cut therein, the tubes are inserted into the holes in the tube sheet, and then the tubes are expanded in the area of the tube sheet so that pressure contact exists between the tubes and the tube sheet.
In the course of normal maintenance or due to malfunctions, it is necessary to replace one or more of the tubes used in a given heat exchange unit. The replacement of a tube requires that the heat exchange unit be removed from the particular cycle in which it is normally employed. Depending upon the installation, the removal of the heat exchanger from operation may result in either inefficient operation or total stoppage of the cycle. Therefore, removal and/or replacement of the tubes must be accomplished as expeditiously as possible.
Previously developed tube pulling devices have utilized a radially expandable jaw, and a plurality of teeth extending annularly about and radially outward from the jaw. An expansion device having a rearwardly tapered wedge longitudinally extends through the radially expandable jaw, and the jaw is expanded by pulling the expansion device towards the back of the tube puller. This relative movement brings a tapered portion of the wedge into contact with the inside of the jaw, and further rearward movement of the wedge forces the teeth of the jaw radially outwardly into the inner surface of the tube to be extracted. Once the teeth securely grip the tube, the jaw is pulled toward the back of the extracting tool, pulling the tube from the tube sheet. The movement in the same direction towards the back of the extracting mechanism, is used to both expand the jaw and pull the tube from the tube sheet.
The previously developed tube pulling devices have not been entirely satisfactory. The jaws may frequently break. Additionally, during the extraction process, while the teeth securely grip the inside wall of the tube and the jaw and teeth are pulled away from the tube sheet to pull the tube therefrom, portions of the tube sidewall are pushed radially inward by the teeth toward the center of the tube. This inward deformation of material decreases the inside diameter of the tube, and the deformed material may scrap or drag against or otherwise interfere with the teeth as the teeth and jaw are withdrawn from the tube. Furthermore, the engagement of the teeth with the tube may cause the tube to deform outwardly, making it more difficult to extract the tube from the tube sheet.
A need has thus arisen for a tube pulling device that operates reliably for the extraction of various sized diameter tubes from a tube sheet. A need has further arisen for a tube pulling device which will automatically control the amount of force exerted by the jaw against the tube during the extraction process.